Aortic aneurysms represent a significant medical problem for the general population. Aneurysms within the aorta presently affect between two and seven percent of the general population and the rate of incidence appears to be increasing. This form of vascular disease is characterized by a degradation in the arterial wall in which the wall weakens and balloons outward by thinning. If untreated, the aneurysm can rupture resulting in death within a short time.
The traditional treatment for patients with an abdominal aortic aneurysm is surgical repair. This is an extensive operation involving transperitoneal or retroperitoneal dissection of the aorta and replacement of the aneurysm with an artificial artery known as a prosthetic graft. This procedure requires exposure of the aorta through an abdominal incision extending from the lower border from the breast bone down to the pubic bone. The aorta is clamped both above and below the aneurysm so that the aneurysm can be opened and the prosthetic graft of approximately the same size as the aorta is sutured in place. Blood flow is then re-established through the prosthetic graft. The operation requires a general anesthesia with a breathing tube, extensive intensive care unit monitoring in the immediate post-operative period along with blood transfusions and stomach and bladder tubes. All of this imposes stress on the cardiovascular system. This is a high-risk surgical procedure with well-recognized morbidity and mortality.
More recently, significantly less invasive clinical approaches to aneurysm repair known as endovascular grafting have been proposed. (See, Parodi, J. C., et al. "Transfemoral Intraluminal Graft Implantation for Abdominal Aortic Aneurysms," 5 Annals of Vascular Surgery, 491 (1991)). Endovascular grafting involves the transluminal placement of a prosthetic arterial graft in the endoluminal position (within the lumen of the artery). By this method, the graft is attached to the internal surface of an arterial wall by means of attachment devices such as balloon expandable stents, one above the aneurysm and a second below the aneurysm.
Although endovascular grafting represents a desirable improvement over traditional surgical repair, current endovascular graft systems suffer from certain deficiencies. For example, current endovascular graft systems do not permit in situ adjustment of length. These graft systems must either be custom ordered or many different sized grafts must be stocked by the physician in order to accommodate the varying sizes of differing patient anatomies. However, it is difficult to custom order a graft system since a patient's vascular system is three-dimensional and tortuous. Therefore, it is difficult for the physician to obtain an accurate measurement. Inventorying many different sizes of graft systems partially solves the problem but is not an acceptable solution because if the wrong size is selected the graft system cannot be modified during the procedure. Additionally, supplying differing sizes of graft systems creates inventory problems for the physician.
One method known in the art for overcoming the problem of an incorrectly sized graft is the use of a separate tubular component to extend a portion of the graft system. However, this requires removing the graft delivery system, opening an additional package with an additional tubular component, preparing the tubular component for insertion, and reinserting a delivery system to add the tubular component. This adds additional steps to the procedure and increases the complexity and time required to complete the repair. Additionally, current endovascular graft systems are not designed to allow a single system to treat a wide range of anatomical lengths.
A further problem associated with current endovascular graft systems is that during deployment the graft system temporarily occludes the aorta, generating a significant downward force. This force makes it difficult to accurately deploy the upper end of the graft system. Such a system is disclosed in U.S. Pat. No. 5,316,023 issued to Palmaz et al.
Thus, a need exists for an improved endovascular graft system which may be adjusted in situ to accommodate the varying vascular systems of different patients without the need to rely on the difficult and often inaccurate measurements of the physician. A need also exists for an endovascular graft system which can be deployed in a manner which does not occlude the artery, thus enhancing the ability to properly place the device.